1. Field of the Invention
This invention relates generally to security inspection systems and more specifically to stand-alone, high throughput inspection systems.
2. Related Art
Security inspection systems are widely used to inspect baggage, parcels or other items before those items are allowed into secured areas. For example, in the U.S., passenger baggage is inspected prior to loading the baggage onto aircraft. In this setting, inspection systems are frequently used to ensure that no baggage containing explosives is loaded onto the aircraft. In addition, security inspection systems may be used to detect other contraband objects, such as drugs, weapons or smuggled currency. Further, security inspection systems may be used in other locations within airports or in other settings where it is desired to create a secured area, such as at cargo terminals or at the perimeters of public spaces.
The challenges that must be met by systems for inspecting baggage to be loaded onto aircraft are representative of challenges that must be met by security inspection systems in many other settings. On the one hand, because of the risk of harm to people and property caused by allowing baggage containing explosives onto an aircraft, the inspection systems must reliably detect contraband. On the other hand, large amounts of baggage frequently must be inspected in short periods of time. Thus, security inspection systems must have a high throughput, which reduces the amount of time available to inspect each item.
To aid in reliably and rapidly inspecting baggage, high throughput baggage systems employ automated image analysis. An imaging unit acquires data on each item to be inspected. This data is correlated spatially to the item under inspection and therefore provides a multi-dimensional representation of the item that can be regarded as an image of the item. Frequently, the data depicts in three-dimensions the density of the item under inspection. Regardless of the form in which information about the item is represented, automated image analysis may be used to detect regions within the image, called “suspicious regions,” having shape density or other characteristics consistent with explosives or other contraband objects. When a suspicious region is detected, an item is said to be “alarmed.” Further processing is required to resolve an alarmed item, either by determining that the item contains no contraband or determining that the item needs to be processed as if it contains contraband.
In some airport settings, security inspection systems are built into the baggage handling system in what is called an in-line configuration. Items move on conveyors to and through the inspection system. Conveyors then move the items to locations selected based on automated analysis performed by the inspection system. The security inspection system interfaces with the baggage handling system controlling the conveyors so that when an item is alarmed, it is automatically diverted by the baggage handling system to a search station for further processing. Further processing at the search station may include human analysis of a visual representation of the image of the alarmed item and, if human analysis of the image is inconclusive, may include a physical search of the item.
In many airports, security inspection systems are not incorporated into the baggage handling system. Rather, they operate in a “stand-alone” configuration. Stand-alone inspection systems may operate in what is called “hold for decision” mode. In this mode, the system processes one bag at a time and if that bag alarms, may hold that bag in its position until a human operator has determined that the bag is “cleared” or is “alarmed” and must be diverted for a higher level inspection. Because bags move through the inspection system sequentially on a conveyor, holding a bag for a decision can stop processing of other bags.
To make a determination on an item, the system displays in visual form an image of the item. When the automated threat detection system identifies a suspicious region, the system automatically displays an alert for a human operator. As part of the alert, the image of the item under inspection is presented to the operator with an indication of regions depicting the suspicious object inside the item. The human operator can then study the image, allowing an operator to make a more sophisticated determination of whether the item may be cleared. If the operator clears an alarmed item, the item may be passed to the baggage loading area. Conversely, if the operator cannot clear the item, a baggage handler will move the item to a search station where the item will be further searched.
In “hold-for-decision” mode, the conveyor stops moving items under inspection when one item is deemed suspicious. By stopping motion of the conveyor, the risk that an item containing contraband will be inadvertently passed to the baggage loading area is greatly reduced.
Inspection systems that can be configured to operate in either hold-for-decision mode or in-line mode are known. One such system has three conveyor stages and two scanning stages. These two stages are a projection X-ray scanner and a CT scanner. The system uses the result from the first scanning stage, which is the projection x-ray stage, to select locations for the second stage, the CT stage, to collect data on “slices” through an item under inspection.
In stand-alone operation, an operator loads bags, one after another, onto a ramped input belt. The system advances the bag to the downstream end of the input belt and holds it there until it is cleared for induction into the projection scanner. As the bags move through the system, the projection scanning section may scan one bag while the CT section is collecting slices on an earlier bag. Because the projection scanner scans a bag faster than the CT scanner, when the projection scanner is done with its bag, it parks it at the end of the projection scanner belt awaiting clearance to inject it into the CT section.
Analysis of the CT slices occurs while the CT scanner is collecting slice data, so an analysis result is often available shortly after the last slice is collected. If, as a result of the analysis, the bag is cleared, the CT section can eject the bag onto an exit ramp. Once the bag in the CT stage is ejected, the bag in the projection section moves into the CT section.
Because bags in both the projection scanner stage and the CT scanner stage are often several feet from their next desired position, after the CT stage determines a screening result, a belt moves the bag at very high speed to maintain throughput. However, once the belt moves a bag in the projection scanner completely out of the projection scanner, the belt slows down to normal scanning speed and the bag on the input ramp moves into the projection scanner, creating the image as it moves through. At the same time, the next bag (already loaded onto the bottom of the input ramp) is moved into position at the top (downstream end) awaiting injection into the projection scanner.
Conversely, if the bag in the CT section is classified as a suspicious bag, that bag remains in the CT section while the operator reviews an image of the bag. As a result, both the CT and projection scanners remain idle until the operator reaches a decision.
Once the operator reaches a decision, regardless of whether the decision is to clear or alarm the bag, the system will eject the bag, using the process described above to advance the bag. If the operator clears the bag, it will be forwarded to its final destination. If the operator alarmed the bag, the operator will take possession of the bag or direct a colleague to do so, so that it can be searched.
One such commercially available system requires an operator to provide a barcode for each bag as bags are being loaded. The system will not inject a bag into the projection scanner until such a barcode is entered, but the rest of the system can continue to work while the input ramp waits on the barcode.
The entered barcode is then associated with the bag image. It is used to track the bag and in some cases is used to influence exactly how the automated system analyzes the bag, including by specifying that the detection algorithm use a more or less sensitive setting. The barcode is also used to recall a bag image on a search station if a bag requires manual searching or other review after the original operator review.
In stand-alone operation, such a system provides good tracking and little opportunity for mistaking an alarmed bag for a cleared one. Because only one bag appears on each scanning belt segment at a time, the display is associated with the next bag to exit the scanner and there is a distinct delay between the ejection of one bag and the next. The system operating in stand-alone mode also provides for good resistance to operator error in input barcodes because the system will hold a bag at the input point until a proper barcode is read. This approach, however, limits the total throughput because each bag is always far from where it needs to be next when the authorization to move is received. The system attempts to address this issue by running its belts at two very different speeds, requiring more expensive motors and controller hardware. Further, the system must be run with a distinct, independent input ramp, which adds costs that are not justified in all cases.
The same type of system may be used in an in-line application. In an in-line application, the system operates in a similar fashion. However, the bag is loaded by an external baggage handling system (BHS) that moves bags throughout the airport. The BHS provides an identifying number (ID) for each bag in place of a barcode (the number may in fact be the barcode of the bag, but does not need to be). The ID is provided as the bag passes a predetermined point in the scanner.
When the BHS delivers a bag to a search station, it can provide the number to the personnel taking possession of the bag via a dedicated number display. The search personnel can then use this number to pull up information about the bag on their search workstation. If the ID is the barcode, it is not necessary for the operator to enter a number because the operator can read the number on the barcode tag.
Another difference between in-line and stand-alone modes is that in in-line mode the bag is not stopped inside the machine if it alarms, but instead progresses along belts controlled by the exterior baggage handling system (BHS), which carries it to a diversion point. If the operator clears the bag before it reaches the diversion point, the bag continues onto the airplane. If the operator does not clear the bag by then (either alarms it or fails to clear it), the BHS diverts the bag to the search room for further processing.
In a networked in-line environment, multiple machines and operator stations are connected together such that one operator can review the images from several scanners or multiple operators can work on the bags from one machine, depending on the rate at which bags are provided for inspection.
In in-line installations, tracking and routing of the bags and correlation of the results to the bags is accomplished via the BHS. These functions are possible because there is no manual intervention in the movement of the bag until it reaches its exit (either at the “plane” or at the search room).
Another commercially available system includes one scanner segment and two radiation tunnel segments. Such a system can be configured to operate in in-line mode, as described above. In a stand-alone mode, operation is different.
Each system has its own conveyor belt. In the most common implementation, the tunnels have a ramped portion of their conveyor that extends from the tunnel and shares the same conveyor belt and motor. Bags can be laid onto the extension and carried into the system on the conveyor. For this system, multiple bags can exist on the input conveyor belt, with a spacing between bags as small as a few inches. As with the previously described system, bags are stopped at the downstream end of the input tunnel and only one bag is allowed to enter the scanner section at a time.
Once the bag is scanned, it moves to the output tunnel and holds there until the system makes an automated decision on whether to clear or alarm the bag. If the system automatically clears the bag, the bag proceeds through the exit tunnel to where it can be manually sent to its destination (such as a loading area for an airplane), and the next bag is injected into the scanner segment.
Conversely, if the system alarms on the bag, the bag continues to wait where it is until the operator renders a decision. If the operator clears the bag, the bag is released and it continues to its destination as above. If the operator alarms on the bag, the operator will take possession of the bag or direct a colleague to do so as it emerges from the exit tunnel, so that it can be searched.
If a barcode is needed for tracking the bag, an operator can input a barcode to be associated with a bag image. The system applies these barcodes in a FIFO manner as the bags are released into the scanner segment. The system does not force the operator to put in a barcode before it will take a bag. However, the input tunnel belt runs only if it has clearance to release a bag at the downstream end. If the belt were to stop to prevent a non-barcoded bag from entering the tunnel, the release of the downstream bag into the scanner could be fouled, making tracking difficult. Consequently, the system is more susceptible to operator error than the previously described system, because the operator could inadvertently insert a bag without a barcode, throwing off the FIFO assignment.
This problem can be avoided by using an input conveyor without the ramp extension and adding a separate input ramp. However, these components add cost and complexity to the product. As with the previously described system, this method provides good tracking and little opportunity for mistaking an alarmed bag for one that has been cleared for loading onto a airplane. However, it processes bags with low throughput. Whenever a bag is transiting the distance from the input tunnel to the scan plane, the system is idle. In standard operation, this idle time limits the throughput to less than half the rate observed on the same system in an “in-line” setting where bags are fed one after the other.
Systems for inspecting carry on baggage are also known. Conventional carry on inspection systems do not make an automated decision, and a decision to alarm or clear a bag is always made by an operator. In a conventional system, baggage is loaded (by the passenger) onto the scanner belt directly. The operator controls the belt motion manually. As images are collected, they are displayed on the screen for the operator to evaluate as they appear. If the operator has not made a decision by the time the next bag starts imaging, the operator will stop the belt and leave it stopped until the operator makes a decision. If the operator decides to clear the bag, he will restart the belt, and the bag will eventually come out to where the passenger can reclaim it. If the operator alarms on the bag, the operator will advance the belt to where the bag is accessible to operator personnel, but not the passenger. The operator or a colleague will then carry out further inspection of that bag based on information about what concerned the operator in the x-ray image.